Ignitor assembly for a percussive type photoflash lamp

ABSTRACT

The anvil component of the ignitor assembly for a percussive type photoflash lamp is provided with segments of different diameter - both of which are smaller than the inside diameter of the hollow metal tube. The smaller-diameter segment of the anvil is supported in centralized position within the tube by a noduled terminus and by four splines that protrude from the largerdiameter segment. The spacing between the smaller-diameter segment and the metal tube is thus increased and premature ignition of the primer material on the anvil during lamp manufacture and subsequent operations is prevented. Forming the splines from a larger-diameter segment of the anvil also provides greater control of the spline dimensions and, thus, better positioning of the anvil within the tube.

United States Patent [191 Buzalski et al.

[ IGNITOR ASSEMBLY FOR A PERCUSSIVE TYPE PHOTOFLASH LAMP [75] Inventors: Bruce T. Buzalski, Dover; Bernard Chauvin, Cedar Grove, both of N.J.;

Henry G. Lay, Bath, NY.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa. 1

22 Filed: Dec.2l, 1972 211 Appl. No.: 317,333

June 28, 1974 Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or Firm-D. S. Huleza [57] ABSTRACT The anvil component of the ignitor assembly for a percussive type photoflash lamp is provided with segments of different diameter both of which are smaller than the inside diameter of the hollow metal tube. The smaller-diameter segment of the anvil is supported in centralized position within the tube by a noduled terminus and by four splines that protrude from the larger-diameter segment. The spacing between the smaller-diameter segment and the metal tube is thus increased and premature ignition of the primer material on the anvil during lamp manufacture and subsequent operations is prevented. Forming the splines from a larger-diameter segment of the anvil also provides greater control of the spline dimensions and, thus, better positioning of the anvil within the tube.

5 Claims, 4 Drawing [Figures IGNITOR ASSEMBLY FOR A PERCUSSIVE TYPE PHOTOFLASH LAMP BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to photoflash lamps and has particular reference to an improved ignitor assembly for photoflash lamps of the percussive type.

. 2. Description of the Prior Art Percussive type photoflash lamps are well known in the art and, in general, consist of an oxygen-filled envelope that contains a charge of shredded metal foil which is ignited by hot particles of primer material when such material is activated. The primer material is located on a metal anvil that is centrally disposed within a hollow tube of thin metal which, when struck by a spring member, is rapidly deformed thus setting off the primer and injecting incandescent particles into the envelope which ignite the metal foil.

It has been the practice in the prior art to form these anvils from a piece of wire having a diameter which is uniform throughout its length and smaller than the inside diameter of anvil tube. The wire anvil is locked within the tube by forming a bead on the end of the anvil and crimping the end of the tube over the bead. Retention of the wire anvil in centralized position within the metal tube was effected by means of protuberances or so-called lobes which were formed on another part of the anvil. A percussive photoflash lamp having a pair of such lobes is disclosed in U.S. Pat. No. 3,616,352.A more recent version of this type anvil wherein two sets of vertically spaced lobes are employed is described in U.S. Pat. No. 3,700,377.

While these prior art ignitor assemblies were generally satisfactoryin that they permitted workable lamps to be manufactured, they left much to be desired with regard to. maintaining the dimensions of the anvil within the tight tolerances required to consistently control the small but very critical spacing between the primer-coated portion of the anvil and the metaltube. If this spacing is too small, accidental ignition during assembly or handling of the finished lamp will occur. If the spacing is too large, the lamp will not fire when the ignitor is struck by the spring. Should the primer on the anvil actually contact the hollow tube, it has been found that even slight vibrations of the type encountered during lamp manufacture and subsequent assembly of the lamps into a multiflash cube unit are sufficient to cause ignition of the primer and lamp. This is particularly troublesome. when ultrasonic energy is used to seal the plastic cover of the cube structure to the plastic base.

SUMMARY OF THE INVENTION The aforesaid difficulties and problems associated with the prior art ignitor assemblies are solved in accordance with the present invention by employing an anvil that has a segment of large diameter and another segment of smaller diameter thus decreasing the amount of swaging required to form the centralizing projections and, at the same time, providing additional clearance between the primer and the hollow tube element of the ignitor assembly. In the preferred embodiment the enlarged terminus is formed is such a manner that it protrudes from an enlarged part of the smalldiameter segment. By modifying the contour of the anvil component in this manner, projections or splines of very small height are required on the large-diameter segment to serve as centralizing means which splines canvery readily be formed and precisely controlled with conventional swaging techniques. The same advantage is derived when the nodule is formed on an enlarged part of the anvil in accordance with the preferred embodiment. The dimensions of small-diameter segment of the anvil can also be controlled to a greater degree than heretofore. The very critical spacing between the primer coating and the hollow tube necessary to provide reliable and consistent ignition is thus readily achieved and the danger of premature or accidental ignition is greatly reduced.

BRIEF DESCRIPTION OF THE DRAWING The invention will become more readily apparent from the exemplary embodiments shown in the accompanying drawing, wherein:

FIG. 1 is an elevational view, on an enlarged scale and partly in section, of a percussive type photo-flash lamp having the improved ignitor assembly of the present invention;

FIG. 2 is an enlarged elevational view of the anvil component employed in the lamp shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view through the splined portion of the anvil, taken along the line IIIIII of FIG. 2, in the direction of the arrows; and,

FIG. 4 is a partial view of another photoflash lamp embodying an alternative form of ignitor structure.

DESCRIPT ION OF THE PREFERRED EMBODIMENTS In FIG. 1 there isshown a percussive photoflash lamp L having a vitreous envelope 12 that is closed at one end by a hermetically sealed hollow metal tube 14 and is tipped off at its opposite end by anipple 16 of fused vitreous material. The envelope 12 is composed of either soft or hard glass, is coated with aprotective film of suitable plastic (not shown) and contains several atmospheres of oxygen and a charge of combustible metal foil 18, such as shredded zicronium or hafnium. Percussively-triggered photoflash lamps of this type are well known in the art and the individual operations required to manufacture them need not, accordingly, be described. The objectives of the present invention are achieved by using an ignitor assembly which consists of an elongated metal anvil 20 that is disposed within the hollow tube 14 and projects into the lampinterior. More specifically, the anvil 20 is so contoured that it has a largediameter segment 21 which extends from the interior of the metal tube 14 into the envelope 12 (as shown in FIG. 1) and merges with a second segment 22 of smaller diameter which is terminated by an enlarged head or nodule 23. The nodule 2.3 has an inwardly flared neck portion 24 which is of the same diameter as the segment 21 and defines a laterally extending ledge or shoulder 25. The noduled end of the anvil 20 is locked in seated engagement with the end of the metal tube 14 by an indented portion 26 of the tube that extends behind the shoulder 25 and thus interlocks with the nodule 23.

As will be noted in FIG. 1, the portion of the anvil segment 21 that is located within the tube 14 has a series of projections or splines 27 formed therein. These splines 27 are of uniform height and length and are circumferentially spaced around the circumference of the anvil so as to provide axially extending passageways for hot particles into the lamp proper when the coating of primer material 28 on the anvil segment 22 is percussively ignited. A suitable bead 29 of refractory or similar material is fused to the anvil 20 adjacent the mouth of the metal tube 14 to provide a deflector for controlling the distribution of the hot particles of primer material that are blown into the envelope.

As shown in FIGS. 2 and 3, the anvil 20 according to the present invention has at least three and preferably four splines 27 that are equidistantly spaced around the circumference of the large-diameter portion 21 of the anvil (that is, approximately 90 apart as in the case of four splines here shown). The splines 27 are swaged from the large-diameter segment 21 of the anvil 20. Hence, they protrude only a short distance (dimension d in FIG. 3) beyond the periphery of the anvil segment 21 and can readily be formed by swaging. More importantly, their height dimensions can be very precisely controlled since only a small quantity of anvil material has to be worked and reshaped in contrast to splines which are formed on a wire anvil of uniform and small diameter. The same is true of the nodule 23 since it is formed on the neck portion 24 which is larger in diameter than the segment 22.

As a specific example, in the case of the percussive photoflash lamp L here shown that is intended for use in a magicube, the anvil had an overall length of approximately 14.6 millimeters. The length of the largediameter segment 21 (including the splines and the adjacent inwardly flared portion) was about 9.1 millimeters, the length of the small-diameter segment 22 was approximately 3.7 millimeters, and the length of the nodule 23 (including the neck portion 24) was about 1.8 millimeters. The diameters of the large-diameter segment 21 and the neck portion 24 were both approximately 1.02 millimeters and that of the small-diameter segment 22 was approximately 0.76 millimeter. The maximum cross-sectional dimensions of the splined and noduled portions of the anvil 20 were both approximately 1.35 millimeters so that each of the splines 27 only projected a distance of about 0.33 millimeters beyond the periphery of the large-diameter segment 21 (see FIG. 3). The inner diameter .of the hollow metal tube 14 was approximately 1.37 millimeters so that the noduled and splined portions of the anvil 20 effected a snug fit with the tube and centrally supported the anvil therein.

To further facilitate the fabrication of the anvil 20, the latter is preferably formed by swaging a suitable strip of sheet metal approximately 0.20 millimeters thick into a hollow tubular member having the aforesaid dimensions. This is a much simpler process to perform than starting with a solid piece of wire having a large diameter and then deforming and swaging it to form a solid anvil having a segment of smaller diameter.

of the metal tube 14a to mechanically lock the anvil 20a in place thus somewhat complicating the assembly operation and presenting somewhat of a risk that the tube 14a, may rupture during the indenting process.

We claim as our invention:

1. In a percussive type photoflash lamp having a vitreous envelope, an improved ignitor assembly comprising the combination of;

a hollow metal tube of substantially uniform diameter sealed to and extending from an end of the lamp envelope, the exposed tip of said tube being hermetically closed and the other end thereof that is sealed to said envelope being open and communicating with the envelope interior,

a metallic elongated anvil disposed and secured in said hollow tube, said anvil having (a) a first segment of substantially uniform circular cross-secton that extends from the interior of said tube into the interior of said envelope and has at least three protruding and circumferentially-spaced splines that are located within the tube and (b) a second segment of substantially uniform circular cross-section that is located entirely within and extends along said hollow tube and is terminated by a protruding nodule the maximum lateral dimension whereof is substantially the same as that of the splined portion of said first segment, and

a layer of primer material on a part of the said second segment of the anvil that is located inwardly from said nodule and splines,

the diameter of said first segment of the anvil being smaller than the inside diameter of said hollow tube,

the diameter of said second segment of the anvil being smaller than that of said first segment, the maximum lateral dimensions of said protruding module and said splined portion being substantially the same as the inside diameter of said hollow metal tube said second segment of the anvil being supported in substantially centrallized spaced position within said hollow tube by said splines and nodule, and

said layer of primer material having a maximum thickness that is less than the spacing between the said second segment of the anvil and the adjacent inner surface of said hollow tube.

2. The invention defined in claim 1 wherein the said first segment of the anvil has four splines that are spaced approximately apart around the circumference of the anvil.

3. The invention defined in claim 1 wherein; said nodule has a neck portion that defines a laterally extending shoulder, and

an indented part of said hollow tube extends behind said shoulder and thus mechanically locks the anvil in operative position within said tube.

4. The invention defined in claim 1 wherein said anvil consists of a swaged tubular member of thin sheet metal.

5. The invention defined in claim 1 wherein said layer of primer material extends around the second segment of said anvil and along a major portion of its length.

l =l l= 

1. In a percussive type photoflash lamp having a vitreous envelope, an improved ignitor assembly comprising the combination of; a hollow metal tube of substantially uniform diameter sealed to and extending from an end of the lamp envelope, the exposed tip of said tube being hermetically closed and the other end thereof that is sealed to said envelope being open and communicatIng with the envelope interior, a metallic elongated anvil disposed and secured in said hollow tube, said anvil having (a) a first segment of substantially uniform circular cross-secton that extends from the interior of said tube into the interior of said envelope and has at least three protruding and circumferentially-spaced splines that are located within the tube and (b) a second segment of substantially uniform circular cross-section that is located entirely within and extends along said hollow tube and is terminated by a protruding nodule the maximum lateral dimension whereof is substantially the same as that of the splined portion of said first segment, and a layer of primer material on a part of the said second segment of the anvil that is located inwardly from said nodule and splines, the diameter of said first segment of the anvil being smaller than the inside diameter of said hollow tube, the diameter of said second segment of the anvil being smaller than that of said first segment, the maximum lateral dimensions of said protruding module and said splined portion being substantially the same as the inside diameter of said hollow metal tube said second segment of the anvil being supported in substantially centrallized spaced position within said hollow tube by said splines and nodule, and said layer of primer material having a maximum thickness that is less than the spacing between the said second segment of the anvil and the adjacent inner surface of said hollow tube.
 2. The invention defined in claim 1 wherein the said first segment of the anvil has four splines that are spaced approximately 90* apart around the circumference of the anvil.
 3. The invention defined in claim 1 wherein; said nodule has a neck portion that defines a laterally extending shoulder, and an indented part of said hollow tube extends behind said shoulder and thus mechanically locks the anvil in operative position within said tube.
 4. The invention defined in claim 1 wherein said anvil consists of a swaged tubular member of thin sheet metal.
 5. The invention defined in claim 1 wherein said layer of primer material extends around the second segment of said anvil and along a major portion of its length. 